Autonomous underwater vehicle looks for algae on underside of ice

Early every spring in Antarctica, mats of algae form on the underside of the sea ice. These mats – along with bacteria that live in them – serve as a food source for zooplankton, essentially kickstarting the food chain for the year. Given that the ice algae plays such an important ecological role, scientists from Denmark's Aarhus University have set out to better understand its distribution. In order to do so, they're using a high-tech underwater drone.

Made by Icelandic firm Teledyne Gavia, the torpedo-shaped Gavia autonomous underwater vehicle (AUV) ordinarily utilizes sonar and a downwards-facing camera to map the sea floor – it's typically used for applications such as searching for submerged objects (including AirAsia flight QZ8501), checking undersea pipelines, or studying bottom sediments.A couple of Gavia AUVs, similar to the one being used in Antarctica (Photo: Teledyne Gavia)

For this study, however, colleagues in Australia modified the AUV to scan upwards with a radiometer. After being lowered into the water through a hole cut in the ice, the vehicle proceeds to autonomously travel along preprogrammed underwater routes, measuring the amount of sunlight shining through the underside of the ice as it does so.

Given that the scientists already know how much light is required for the algae to grow, these measurements allow them to figure out where the colonies are likely to be present. In order to check the accuracy of these extrapolations, ice core samples are periodically extracted from scanned areas, and their algae content is compared to the predicted amounts.

According to the university, use of the Gavia has allowed for mapping the distribution of ice algae "over very large areas where studies have not previously been possible." Such work would otherwise have to be performed by scuba divers, who would be limited by their air supply and other factors.

Due to the promising initial results, plans call for an AUV to be also used in an upcoming study of ice algae in the Arctic.